The supplements were found to reduce the risk of asthma attacks by half, but Dr Chris hailed the vitamin’s overall boost to the immune system.

His comments came after vitamin D was found to protect against severe asthma attacks, which were more common during winter.

The study, by researchers at Queen Mary University of London, found that people who took oral vitamin D supplements, in addition to standard asthma medication, could halve their risk of an asthma attack which required going to hospital.

The vitamin boosted the immune response to respiratory viruses, and cut down harmful airway inflammation, the researchers found.

“Vitamin D has a fascinating impact. A pill, costing just 2p, reduces asthma by 50 per cent,” said Dr Chris on ITV’s This Morning.

“It reduces steroid treatment - the most severe treatment - by a third.

“Of course, vitamin D is good for the whole immune system. It reduces inflammation, and protects against cardiovascular disease and MS.

“Taking normal doses of the supplement has no adverse effects, either.”

The Vitamin D Council claimed it wasn’t possible to get enough vitamin D from diet alone, as natural levels in food has dropped.

Symptoms of vitamin D deficiency include frequent infections, tiredness and general body pains. Those most likely to have a deficiency include those spending lots of time indoors, pregnant women, and those who are overweight.